Real-time Audio
Spectrum Analyzer

Use your Sound Card and the
"Audio Test Set" from SatSignal Software

Output Features Generate sweep tones, continuous tones,  sinewave, triangle, white & pink noise
Input Features Vectorscope, time domain scope, spectrum analysis
Analysis Features Tracking Generator sweeps output tone and measures input in full duplex
Measurement Uses Measuring balance, frequency response, filter characteristics, microphone response, speaker output quality, finding noise floor in audio devices, and more
Educational Value Learn about Audio devices, how to evaluate quality, dynamic range, distortion
Compare Prices If you price a bench-top Audio Spectrum Analyzer with Tracking Generator you'd see they cost literally thousands of dollars.

With your full duplex sound card, and the Audio Test Set you can do almost all of the audio analysis you can with an expensive Audio Spectrum Analyser.

It's free!  Download here.  You may also need to download and install my runtime Library Bundle if you don't already have it.  I've added an RTF version of the Help file for newer Windows systems.

If you like it, you can register it as a "thank you".


Audio Spectrum Analysis of Sine Wave

This is a view of the Real Time Generator/Analyzer Screen
The audio is a single sinewave Tone, at 550 Hz
The Tone is coming out of the speakers attached to the sound card
The Analyzer input is the MIC input
Notice the peak at 550 Hz, with an apparent roll-off
The roll-off is due to the bandwidth of the Analyzer
The Hz scale (Horizontal) has been widened (user defined)
to show that even at about 50 Hz on either side of 550 Hz
the signal shown is about 40 db down from the peak.


Audio Spectrum Analysis of Triangle Wave

This is a single tone, but the waveform is a TRIANGLE.
Notice the harmonics appearing at 3, 5, 7, 9 ... times the base 1 kHz

The left side of the program is generating audio which is being played
into a cheap set of speakers, using max audio volume and midrange
wav level, and midrange treble and bass. This audio then goes into
an inexpensive microphone with 20 db gain set, maximum level
One user noted that this spectrum plot looks more like a square wave
than a triangle, so we are assuming that the speaker, microphone and
settings used have distorted the triangle into more of a square wave

The sound card mixer settings are obviously important
and the characteristics of the output and input devices
are also going to affect the measurements.

Sound card is a Creative Labs Sound Blaster Live Value card
Speakers are some inexpensive MS 691 Multi-Media 2" speakers
Microphone is a Labtec AM-242 plastic boom mic


Audio Spectrum Analysis of Two Tone signal

This is a pair of tones. The Left speaker is about 6 inches from the mic
and the Right speaker is about 1 inch from the mic
Notice the relative amplitude of the two tones, showing the lower amplitude
of the 550 Hz tone, which could be due to (1) the distance of the speaker from the MIC
and/or (2) the frequency response of the speaker/mic combination


Audio Frequency Response using Tracking Generator and Spectrum Analyzer

This is a sweep tone from 100 Hz to 1000 Hz, and the frequency response of the speaker/mic
system on my computer. Notice the ramp up to about 175 Hz, a roll-off, then
a steady rise to about 370 Hz, then a roll-off to -20 db from 550 Hz to 1000 Hz

Note: In this mode, the Tone Generator and Spectrum Analyzer are "Tracking"
This is useful for testing frequency response characteristics


Audio Spectrogram of Music Sound Source
This is a spectrogram of some piano music called
"The Entertainer"
Here's what you're seeing in the spectrogram:
The horizontal axis is time, the display is "sliding" to the left over time.
On the vertical axis is "Energy" at the frequencies indicated
Notice the energy comes on the "beats" in the music
and you can see the notes played are repeated
Listen to the clip (link above) and look at the spectrogram
You'll get an idea of what this display means

Copyright © David Taylor, Edinburgh   Last modified: 2019 Nov 01 at 10:41